Hydraulic drilling machine



Dec. 29, 1936. E. J. HIRVONEN I 6 HYDRAULIC DRILLING MACHINE Filed Nov. 30, 1934 2 Sheets-Sheet l Dec. 29, 1936. E. J. HIRVONEN 2,066,109

I HYDRAULIC DRILLING MACHINE I Filed Nov. 50, 1954 2 Sheets-Sheet 2 Inverzfoifi '20 the required depth of hole I Patented Dec. 29, 1936 UNITED STATES PATENT OFFICE v 2.066.109 HYDRAULIC DRILLING MACHINE Eric J. Hirvonen, Worcester, Mass., assignor to Leland-'Giflord Company, Worcester, Mass, a corporation of Massachusetts Application November 30, 1934, Serial No. 755,405

4 Claims. (01. 121-45) from the work, at least theslow advance or cut-' ting, speed being maintained constant regardless of variations of work resistance. Such a machine 10 is disclosed, for instance, in my copending application Serial No. 636,855, filed October 8, 1932,

wherein the drill is advanced rapidly from a fully retracted position to a work engaging position and is then advanced slowly at a constant rate of speed into the work for a predetermined depth and then is retracted rapidly to a point wherein the drill clears the work, for the purpose of removing chips from the drill hole, and then is readvanced rapidly to the bottom of the hole and at slow speed again into the work and so on until has been drilled, whereupon the drill is retracted rapidly to a fully retracted position. The drill is thus progressively advanced further into the work at each slow speed or working part of the stroke.

25 Some of the advantages of such a machine are the rapidity with which .the machine functions and the accuracy of control of the speed of movement of the drill and the positions where the drill speed changes or reverses. Such advantages are 80 obtained, however, only when the hydraulic cylinder that efl'ects the advancementand retraction of the drill is free from air so that the cylinder on opposite sides of the piston is at all times filled with oil and is free from any sensible amount of 35 air that by reason of its elasticity prevents the drill from advancing at a constant determined rate and delaysthe speed changing of the drill.

The effects of entrapped air are particularly noticeable in a machine wherein the hydraulic cyll inder and piston are vertical.

.An object of the present invention is a hydraulically actuated machine tool, as a 7 ng machine, provided with hydraulic mechanism for operating the drill in a series '01 definite cycles each including movement or the drill at difl'erent speeds, an advancement oi the drill into the work at con-' staut speed, irrespective of variations of work resistance, and preferably also progressively inv creased distances of advance, combined with m'eans for eflecting the removal of air from the cylinder that reciprocates the drill in this manner.

"A further object of the invention is the provision of a hydraulic actuating system for a drilling machine or the like wherein the piston is provided with an air bleed passage through which air that is entrapped in the-lower end of the cylinder under the piston can pass into the upper portion of the cylinder and escape from the system without at the same time causing an appreciable loss 5 of oil from the lower portion and also without at the same time losing oil that materially afiects the rate of movement of the piston.

A further object is generally to improve theconstruction and operation of hydraulically actuated machine tools.

Fig. 1 is a perspective view of a hydraulic drilling machine embodying the present invention.

Fig. 2 is a diagrammatic view of the hydraulic system including the cylinder and piston for reciprocating'the drill spindle of the machine of Fig. 1. Fig. 3 is an enlarged sectional detail of the piston and cylinder of Fig. 2 and illustrating more clearly the air bleed valve forming a part of the present invention. 1

Fig. 4 is an exploded view of the valve structure ofFig.3.'

Figs. 5 and 6 are sectional views taken respectively along lines 55 and 6 6, respectively, of

Fig. 3.

The drilling machine embodying the present invention, and as illustrated in Fig. 1, comprises a vertical frame l0 which supports a spindle driving motor l2. The motor shaft H has a sliding driving connection with the vertical drill spindle I6 carried by a vertically reciprocating carriage l8. A drill, not shown, is adapted to be carried by the lower end of the drill spindle l6. and to be reciprocated into and out of engage- 36 ment with work supported upon a vertically adjustable table 20. The carriage l8fis reciprocated by means including the hydraulic cylinder 22. The hydraulic cylinder, see particularly Fig.

2, containsa piston 24 which is fixed to the upper end of a piston rod 26 that passes through a stufllng box 28 at the lower end of the cylinder, the lower end of said piston rod being fixed rigidly to the carriage l8 by suitable means as the bolt 30. Thus the carriage is constrained to reciprocate withthe piston. The carriage I8 has movable with it a cam plate 32 which, in Fig. 1, is contained within the control box 34. A cam block 36 is carried by and is at times recipro cable with said plate 32 and at other times held stationary while said cam plate continues to move for the purpose of obtaining successively advanced feeding strokes and also for resetting the cam block at the end of the operating cycle. The

v particular manner in which this is accomplished is set forth in my above referred to application but is not necessary to be described in detail for an understanding of the present invention. The cam block 38 is provided with horizontal or dwell portions 38, 38 and 42 connected by inclined cam portions 44 and 48, respectively. A valve-mechanism control shaft 48 is provided with a camoperated arm 58 having a laterally extended pin 52 that cooperates with the aforesaid dwell por tions and cam surfaces. When the pin is on the dwell portion 38 the arrangement is such that the piston and drill are advancing at fast speed advance toward the work. When the cam portion 44- engages the pin and raises it from the uppermost dotted position to the full line position the control shaft sets valve mechanism to slow down the speed of the piston and drill and cause the drill to advance at slow or cutting speed. Said pin also serves to hold the cam plate stationary relative to the advancing cam plate 32. When the cam plate has moved a predetermined distance the cam surface 48, which is movable independently of the cam block, causes the arm 58 to be thrown downwardly into the lowermost dotted line position, thereby to effect the rapid retraction of the piston and drill. The cam plate 32 is provided at one end thereof with a cam block 54 having a cam surface 58 that in the fully retracted position of the piston and drill engages the pin 52 and moves it from the lowermost dotted line position into the next uppermost position. This position is a,neutral position of the control .arm and the mechanism controlled by said arm causes the piston to be held stationary in the fully retracted position determined by the setting of the cam block 54. The control arm 58 with its shaft 48 can be thrown forwardly into starting position manually by the operation of the control lever 58, see Fig. 1, and also by the operation of a control valve 88, Fig. 2. A spring pressed plunger 82 is operative on the shaft 48 to move the shaft rapidly from slow speed advance into reverse positions and also -to hold the shaft positively in both fast advance and slow advance positions.

The-hydraulic control mechanism for the piston and cylinder, indicated generally by the nu- V meral 83 in Fig. 1, includes a valve cylinder 84 having a double piston 88, 88 therein. The valve cylinder receives high pressure oil through a port I I8, which in the fast and slow advance settings of the valve piston is disposed between the piston 88, 88. High pressure oil is supplied to the port I8 through a pipe 12 from an accumulator 14 which is supplied with oil through a constantly operating oil pump reservoir 18. In the drill-advance setting of the piston 88, 88, oil can pass freely from the inlet port 18 through the outlet port 88 into the inlet port 82 of a speed regulating cylinder 84 having a double piston valve 88, 88 therein. In the normal position of the valve pressure oil passes from the port 82 along the valve cylinder .1 and out of the port 88 into the passage 82 and thence into the upper end of the cylinder where it acts upon the piston 24 in a direction to move it downwardly toward the work. The cylinder under the piston, in the normal operation of the machine, is adapted to be completely full of oil, which oil is forced out of the lower side of the cylinder through a pipe I8 by the greater piston pressure set up by the pressure of oil on the upper side of the piston, the oil flowing through the passage 84 and the stunned to flow from the to its extreme right Infully retracted 18 drawing oil from an oil 88 and into the reservoir and accurate response port 98 into the right hand end of the valve cylinder 84 where the oil escapes.

The condition above described is that which causes the piston to advance rapidly toward the work. When the piston has advanced so as to bring the drill almost into engagement with the work the valve piston 88, 88 is moved towards the right by the action of the aforesaid cam block 38 to partly restrict the outlet port 88 and to close the. exhaust port 88. Oil pressure on the under side of-the piston is then built up because the oil outlet is res ricted, the oil now being con=- passage 84 into the valve cylinder through a restricted'passage I88 controlled by a speed setting valve I82. The setting of this valve determines the rate at which the piston can advance. The increased pressure in the under side of the cylinder'acts through a restricted passage I84 connected with the passage 94 to apply pressure to the left hand end of the speed regulating piston 88. This pressure opposes the pressure of the spring I88 and a balance is established with the piston 88 partly throttling the inlet port 82. The pressure on the underside of the piston varies with varying .work resistance and the valve 88 operates to vary the opening of the port 82 in such manner as to admit oil to the upper side of the piston to maintain the rate of slow speed advance of the piston constant regardless of variations in work resistance. When the control valve 88, 88 is moved hand position, for rapid retum of the'piston and drill, the piston 88 is disposed between the ports I8 and '88 and the piston 88 is disposed at the right hand side of the port 98. Under these conditions pressure 011 can flow from the portion 18 into the port 88 and thence into the under side of the cylinder while the upper side of the cylinder is in communication through the port 88 and the waste passage I88 with the oil reservoir. Thus the piston is retracted rapidly into fully retracted position. position the piston valve 88, 88 is moved into a position where the piston 88 covers the port 88 and the piston 88 covers the port 88 and the outlet end of the passage I88, thereby sealing the oil in sides of the piston against escape.

The piston valve 88, 88 is operated by the reciprocating member II8 actuated by an arm II2 fixed to the shaft 48. The piston valve is alsomoved into positions for eflecting advance and also retraction of the drill by a cylinder 4 having pistons H8 and 8 respectively that are engageable with a part of the member II8,"the pistons being actuated by a fluid pressure under control of the manually operated valve and also under control of mechanism I28 for eifecting the advance of the drill from an intermediate retracted position, and also a device I22 responsive to excess work resistance for eflecting the repeated retraction of the drill from the work, not necessary to explain in detail here.

The system as thus described depends mainly for its accuracy of operation and rapid response to changes in the settings of the control valves to the incompressibility of the hydraulic actuating fluid and the absence of air from the cylinder 22. Air is always present in the ducts and piping after the machine has been out of operation for an extended period and it is highly desirable to purge the system from air in order that prompt of the piston may result from the change of settlngp the control valves. For instance, the feed of th drill is maintained the cylinder on both sure of the entrapped oil on the piston at times when the pressure should be variable. For the same reason the expansion of the entrapped compressed bubble causes the tool to jump forward when it breaks through the work. The response of the piston to changes of settings of the control valves is also slow due to the bubble since the variations of pressure are absorbed in compressing or permitting the expansion of the bubble; and the tool will hang at a certain set ting where it should instantly change its speed and advance at the changed speed.

In accordance with this invention means are provided to purge the cylinder'22 from entrapped air and especially from air that may be entrapped in the lower part of the cylinder under the piston especially since the cylinder and piston are vertically disposed. The purging means comprises a valve structure I24 located in the piston 24 and establishing communication between the oil spaces in the cylinder on opposite sides of the piston. Said valve structure is illustrated more particularly in Figs. 3 through 6. Said valve structure comprises a bushing I26- which is inserted in a hole I28 passing through the web of the piston and is an oil tight pressure fit therein. The bushing I26 is provided at one end with a. small diameter axially disposed bleed passage I3It which opens into a larger coaxial passage I32 that extends to the other end of the bushing. A conical valve seat I34 forms the junction between the two passages. A valve member I36 is located in said bushing, the valve having a stem I 38 which is disposed loosely in the small passage I30 and an enlarged head I40 which is disposed in the large passage I 32. The head is also formed with a conical face I 42 which is adapted to rest upon the valve seat I34 of the bushing to close the bleed passage. A shell I44 is pressed in the passage I32 above the head of the valve to retain the valve in place, the inner end of the shell being sufiiciently spaced from the head of the valve member'to allow the valve member to operate, and the inner end having transverse slots I46 that permit fluid to pass from the valve chamber I 32 into the axial passage I48 of the shell when the head of the valve is in contact with the inner end of the shell. The small passage I30 of the bushing is adapted to be slightly larger in diameter than that of said valve stem I39 and the difference in diameters provides a bleed passage of small cross section and also one of large surface through which the air entrapped in the under side of the piston can pass through the piston.

The area of the bleed passage, however, is adapted to be sufllciently small so that the amount of oil that can pass through the passage at .each rapid return traverse of the piston is negligibly small, the relatively large surface of the passage tending to keep down the flow of oil. In practice for a cylinder of two inches diameter it has been found satisfactory to have about five thousandths of an inch difference in diameter between the valve stem and the passage III; with a valve stem diameter of about thirty-five thousandths of an inch. The bleed small in area.

When the system is first put in operation the actuating cylinder 22 and the oil ducts commudownward stroke of the piston in a working direction' there may be both pressure oil and compressed air in the upper part of the cylinder and air maybe in the lower part of the cylinder and compressed under the downwardly moving piston, the air being driven out through the pipe 92 and "the port 96. The high speed advance position of the first stroke of the piston is thus more rapid than is intended since the air can escape much more freely than oil. When the piston reaches a point in its travel where the regulating valve is moved from thehigh speed to the low speed adpassagethus is seen to be very 1 nicating therewith contain air. On the first van'ce position the escape of air from the under side of the piston is retarded but still can escape much faster than oil through the regulating passage IIIO and usually suiliciently fast so that there is not enough back pressure set up to operate the constant speed valve 86, 88. Thus the rate of slow speed advance is also greater than desired. When, however, the piston reaches the bottom of its stroke and pressure oil is admitted to the under side of the piston and the cylinder above the piston is vented freely to the oil reservoir I8 and to the atmosphere the pressure oil flowing into the lower part of the cylinder forces the entrapped air through the valve structure I24 into the upper part of the cylinder where the air can escape through the relatively short passages 92 and the valve ports to the atmosphere. It might be stated that in practice waste passages 98 and I08 are omitted, the valve cylinder 64' being freely open at the ends to the atmosphere, although in a confined space where the oil is collected and returned in the oil reservoir I8 so that the passages through which the escaping air can pass to the atmosphere are, relatively short; The entrapped air in the lower end of the cylinder is largely expelled therefrom in the first return stroke of the piston. In any event after one or two strokes the system becomes completely filled with oil and the apparatus functions in the normal intended manthrough the body of oil contained in the upper end of the cylinder between the piston and the entrance to the passage 92 so that the air is forced ahead of the oil, the volume of oil in the cylinder above the piston being more than sufiicient to fill the outlet passages, and hence the first stroke is suflicient ordinarily to completely fill the working side of the cylinder with oil. While the valve structure I24 is open on each return traverse of the piston due to the greater pressure of oil under the piston than on top of the piston, the bleed area through the valve structure is so small that the amount of oil that can escape is negligible and does not put any sensibly increased demand upon the accumulator 14 or the pump IS. The small amount of oilthat can pass through the valve structure during the return traverse is, however, 'of no importance in so far as efi'ecting the speed of the piston is concerned, since precise uniformity of rate of speed of the return traverse is not necessary. The bleed passage through the valve structure, however, is sealed on the working traverse of'the piston and hence there is no' csand thus the associated valve cture can main-- 7;

tain an unvarying predetermined rate of advance of the piston and associated drill.

I claim:

1. Hydrauiically actuated mechanism comprising a cylinder, a piston therein, a piston rod connected therewith, means including a valve mechanism for admitting pressure hydraulic fluid to and the escape of fluid from the opposite ends of said cylinder alternately, said piston having a passage therethrough, and a valve that opens and closes said passage in response to pressures on opposite sides of said piston, said valve having a flow-restricting stem in said passage having a cross-sectional area slightly less than that 01' said passage and thereby restricting the flow of fluid in said passage.

2. Hydraulically actuated mechanism comprising a cylinder, a. piston therein, a piston rod connected therewith, means including a valve mechanism for admitting pressure hydraulic fluid to and the escape of fluid from the opposite ends of said cylinder alternately, and means for purging said cylinder at least on one side of said piston from entrapped air, said means comprising a ilalve structure including a bushing located in a passage extended through opposite faces of said piston, said bushing having an axially-directed small bleed passage extended thereinto from one end, an axially-directed large passage extended into said bushing from the other end and opening into said bleed passage, a valve having a head in said large passage and seating over theinner end of said bleed passage and having a stem movable axially in said bleed passage, said stem being but slightly smaller in diameter than the diameter of said bleed passage whereby the clearance passage between the stem and passage has small area and large surface, and a shell in said large passage confronting said valve head and 2,oce,1oe

defining the open position of said valve and hav ing an inner end notch opening into a central Passage therethrough. 1

' 3. .Hydraulically actuated mechanism'comprising a cylinder, a piston therein, valve mechanism for controlling the flow of a hydraulic fluidiinto andout of said cylinder on ,opposite sides 01' said piston, and means for purging said cylinder at least on one side of the said pistonoi air comprising a bushing in said piston having a small a diameter fluid passage therethrough open to opposite sides of said piston, a tree valve in said passage controlling the flow oi fluid therethrough and opening and closing in response to fluid pressure differences on opposite sides of it, said valve having a stem movable axially in said passage and being only slightly smaller in diameter than the diameter of said passage, the space between said stem and passage constituting an air purging passage, and a valve-retaining shell in said passage having notched end confronting and spaced from said .valve and constituting a stop member defining the open position of said valve, said shell having a fluid passage therethrough.

4. The combination with a hydraulically operated cylinder and piston, of. means for purging air from the cylinder on one side of the piston into the cylinder on the other side of the piston while preventing deleterious flow or hydraulic liquid through said purging means, said purging means comprising a small diameter passage of short" axial length through said piston, a stem in said passage having but slightly less diameter than the diameter of said passage whereby to provide an annular flow path of small thickness and large surface, and means for reciprocating said stem agially of said passage to keep it clear of obstruction. ERIC J. HIRVONEN. 

